Heat exchanger and method of making same



March 21, 1939. A. VARGA HEAT EXCHANGER AND METHOD OF MAKING SAME FiledJune 12, 1936 Patented Mar. 21, 1939 PATENT OFFICE HEAT EXEHANGER ANDMETHOD OF MAK- ING SAIHE Alexander Varga, Budapest, Hungary ApplicationJune 12, 1936, Serial No. 84,936

In Hungary June 19, 1935 5 Claims.

exchangers serving for transmitting heat from.

one gaseous or liquid medium to another medium of 'a similar character.In most cases the heat transmission coefiicients of the. two media aredifierent. In the case of boilers" for instance a gaseous medium '(smokegas) flows on one side and liquid medium (water) on the other side ofthe heat exchanger tube. Water is known to possess a far higher heattransmission coefiicient (about the hundred-fold) than gaseoussubstances and consequently the water could take up far more heat fromthe heat transmission wall, than the wall is capable of taking up fromthe smoke gases. Since the quantity of heat transmitted is proportionalto the area of the heat transmitting wall, the size of this wall isalways adapted,

' in order to avoid this, the high heat conductivity of the metals isutilized in this sense that that side of the heat transmission wall,which is in contact with the medium having a lower heat transmissioncoefficient, is enlarged in order to increase its heat absorbingcapacity. In this manner it is possible to transmit onto one and thesame volume the double and in some cases even the treble of the quantityof heat.

In actual practice the increasing of the heat transmitting area (theheating or cooling surface) is attained by means of a system of ribssuch as are present for instance in the radiators of motorcars and roomheating systems, in economizers etc. Hitherto, however, with a singleexception, of which more shall be said herebelcw,

these ribs have always been mounted on the outer surface of the tubes.Apart from the fact that such outer rib systems can only be produced bycasting, which means high first cost, these sys-' be used in view oftheir insufiicient strength. However, if the outer medium has the higherheat transmission coeflicient, their use would also be useless. It hastherefore been suggested to fit the groups of smoke tubes in locomotiveboilers, which formerly were always designed as plain tubes, with innerribs (Serve tubes), in which, as shown in the uppermost tube in thesystem of tubes shown in Fig. 1 of the drawing afiixed to thisspecification and forming part thereof, the tube wall a is fitted withradial inwardly directed ribs b, the surfaces of which serve to enlargethe heat absorption surfaces in contact with the inner medium of lowerheat transmission coefiicient. However, such tubes have not come up toexpectations, since in view of the inner radial ribs formingconstrictions and bailles they were clogged after a short time by thesoot accumulating therein. Apart therefrom, the spaces 0 left betweeneach adjoining pair of tubes form undesirable constrictions of the heattransmission area.

In the heat transmission bodies according to the present invention allthese drawbacks are avoided. Such body is formed of a single outer wallof oblong closed cross section, which replaces a system of superposed orjuxtaposed tubes as hitherto provided, and of inner ribs or partitionsextending from the inner wall of this body and partly or altogetherbridging the space between its two walls, thereby forming a plurality ofsuperposed or juxtaposed conduits.

In this heat transmission body the individual conduits directly adjoineach other, so that the group of tubes or conduits formed in such bodyis not separated by undesirable spaces such as the spaces 0 in Fig. 1.Since the ribs themselves now form the walls of the conduits, no bafflesleading to the accumulation of ,soot are present in such body.Preferably the inner ribs are so dimensioned, that they not only enlargethe heat absorption area of the outer wall, but also act towards bracingthe outer walls of the body, which is important in the case where theouter heat exchanging medium is under increased pressure.

Obviously a heat transmission body according to this invention will beuseful not only in connection with boilers, but in a general way in alldevices serving to bring about an exchange of 6 by casting, by formingthe conduits in a solid blank having the outer configuration of theouter wall, by producing therein the conduits by boring, milling orpressing. -It may further be produced from two halves, in which theconduits may be produced by planing and the like.

My invention also relates to all the methods, whereby such a heattransmission body can be producedln a simple, inexpensive and eilicientmanner and can be fitted in the tube supporting walls.

Idgs. 2 to 9 of the drawing illustrate some embodiments of my invention.

In the drawing,

Fig. 1 is a atic end view of a tube assembly- Fig. 2 is a perspectiveview of the first embodiment.

Fig. 3 is a similar view of a heat transmission body with outwardlycurved side walls for each conduit.

Fig. 4 illustrates the production of such heat transmission body from apair of rolled plates, while Fig. 5 illustrates the production of thebody from a pair of metal sheets, to which the ribs have been fixed bywelding.

Fig. 6 is an axial longitudinal section of such body with expansion gapsprovided on the ribs.

Fig. '7 illustrates the method of interconnecting the main parts of aheat transmission body of great width by welding.

Fig. 8 is an axial section of one end of a heat transmission bodyshowing a way in which such end is fixed in place in the wall, and

Fig. 9 illustrates another mode of fixing the end of such body in suchwall in a resilient manner.

Referring to the drawing and first to Fig. 2, I is the outer tube wallof oblong cross section and 2, 2 are transverse ribs mounted on theinner side of the tube wall I, these ribs serving to take up andtransmit onto the wall I part of the heat of the medium fiowing in theconduits 3 and 4 formed between the ribs, these latter at the same timebracing the outer wall I. Each pair of adjoining ribs 2 forms a conduit3 of rectangular cross section, the two end conduits having asemicircular cross section and the conduits 3, I together replacing asystem of tubes as hitherto used.

A heat transmission body of this kind may be produced by rolling andwelding.

Fig. 4 illustrates a pair of rolled plates I, I before the butt endshave been connected by welding. The heat transmission body is composedof two symmetrical halves produced by rolling, each half representing anumber of juxtaposed T- or U- (channel) irons, the bases formingtogether the side wall of the body, while their free webs form a rib 2.The base portions 5 at either end of each half are bent into circularsegments. If these two rolled halves are assembled with their ribsfacing each other and abutting against each other, and if the butt ends6 of the curved parts 5 are now connected by welding, the heattransmission body is finished and no connection by welding or otherwiseis required between the ribs, since as a rule such a body is acted uponby an outer pressure, whereby the abutting ends of the ribs are forcedonto each other, the longitudinal outer walls I being thereby enabled totake up a pressure of 15 to atmospheres.

In order to enable the outer wall to withstand higher pressures, it maybe curved outwardly between theindividual ribs as shown in Fig. 3.

If the butt ends of the ribs are also connected by welding, a heattransmission body of this kind may also take up an inner pressure.

It is also possible to produce such a body by welding exclusively. asshown for instance in Fig. 5, where ribs 2 are fixed to the plates Iforming the outer walls by welding along the edges at 1. However, herethe ribs are preferably not arranged to abut against each other, but aremounted on the walls in staggered relation, the ribs of one half Iextending between the ribs of the other half, since in this manner muchwelding work can be saved. With welded ribs such as here shown heattransmission bodies of any desired width may be produced.

It is, however, also possible to produce bodies with rolled side wallsand ribs for greater width, if proceeding in the manner shown in Fig.'I. Here the rolled side walls I may be formed with abutting or withrelatively staggered ribs according to Fig. 4 or 5. However, since therolling of very large bodies is connected with difficulties, the ends ofthe body are here preferably formed by separate end portions 8 ofsemi-circular section, which are not rolled in one piece with the sidewalls I, but are bent each from a separate plate or drawn after themanner of tubes. The straight edge portions 9 of these separate parts 8form the ribs. These parts 8 are connected with the rolled side walls Iat III by welding.

Since the ribs of the heat transmission body conduct the heat taken upby them in the direction of their width to the point where the heat isdelivered on a longer path than the side walls I (in the direction oftheir thickness), the temperature of the ribs will be higher than thatof the side walls. In view of the expansions taking place, owing to thisdifference in temperature, the ribs, as shown in Fig. 6, are preferablyformed with indentures I I produced for instance by sawing, theseindentures forming expansion gaps.

In thetube supporting wall I3 a heat transmission body of the kind abovedescribed may be mounted for instance in the manner illustrated in Fig.8, where the end I2 of the body is shown as being fixed in the wall I3by forming a welding seam I4 all around the end of the body. In thecase, where the tube is particularly large, I prefer providing for therequired expansion by fixing the body in the wall in the manner shown inFig. 9, where a piece of the ribs I5 at the end I2 of the body is cutoff and the open edges of the side walls I are bent outwardly in heatedcondition to form a ring I6 of semi-circular cross section, the radiusof which is chosen in accordance with the desired spring action, thisring being then fixed to the wall I8 by means of a welding seam II. Ifsuch heat transmission body shall be replaced by another one, thewelding seams are removed with the aid of the chisel and the bent edgeportions I6 are rebent, whereafter the body can be withdrawn from thesupporting wall and replaced by another one.

In the case of gases and liquids with lower temperature, and moreparticularly in the case of condensers, the fluid-tight fixing of theheat transmission body in the wall may be effected by means of astufiing box.

Various changes may be made in the details disclosed in the foregoingspecification without departing from the invention or sacrificing theadvantages thereof.

I claim:

1. A tubular heat exchange body, particularly adapted for use inconnection with smoke tube boilers and of the type affording passage onthe inside for a gaseous medium, and on the outside for a liquid medium,comprising in combination a pair of rolled metal wall portions arrangedin parallel spaced relation, curved end portions having a continuoussmooth surface both on their inside and outside associated with saidwall portions, welds joining together the abutting edges of said curvedsmooth end portions, each of said walls including a plurality ofsubstantially parallel ribs formed integral therewith and projectinginto the interior of said body, the two sets of ribs being juxtaposed sothat the ribs associated with opposite walls abut against each other,said abutting ribs forming partitions subdividing the interior of saidbody into a plurality of conduits adapted as passages for said gaseousmedium.

2. The heat exchange body of claim 1, wherein the end portionsassociated with each of the rolled metal wall portions are curvedsubstantially through a quarter circle, the edges of each juxtaposedpair of end portions abutting against each other, and a weld joiningsaid abutting portions together.

3. The heat transmission body of claim 1, in which heat expansion gapsare provided in the ribs.

4. The metallic heat transmission body of claim 1, in which separatecurved end pieces with inwardly projecting ends bridge the spaceenclosed between the metal walls.

5. The method of producing a tubular heat exchange body particularlyadapted for use in connection with smoke tube boilers and of the typeaffording passage on the inside for a gaseous medium, and on the outsidefor a liquid medium, which comprises rolling separate halves of saidbody each of which includes a metal wall portion, curved end portionshaving a continuous smooth surface both on the inside and on the outsideand a plurality of substantially parallel ribs extending at asubstantially right angle from said wall portion, all in one piece, andwelding together the abutting edges of each two juxtaposed end portionsso as to firmly unite the two halves of the body.

ALEXANDER VARGA.

